Some printing systems have a service cartridge that comprises several different types of functional areas or units, including e.g. a web wipe, which is a web of wiping material to wipe the lower surface of the printhead, and a spittoon unit on which the printhead may spit drops of printing fluid, such as ink. The printing fluid spat by the printheads, together with that discharged in priming operations, is collected in a printing fluid storage container which takes up a portion of the volume of the service cartridge.
When one of the functional units of the cartridge becomes exhausted the service cartridge should be discarded or recycled, and replaced with a fresh one. In some cases the web wipe may be consumed before the printing fluid storage container is full, and it may be used as an indicator of the overall life of the cartridge. The web wipe consumption may be tracked to determine when the cartridge needs to be replaced.